Analytical Characterization of Water-Soluble Constituents in Olive-Derived By-Products.

Pablo Doménech,Aleta Duque,Paloma Manzanares,Isabel Higueras,José Luis Fernández

doi:10.3390/foods10061299

Abstract

Olive trees constitute one of the largest agroindustries in the Mediterranean area, and their cultivation generates a diverse pool of biomass by-products such as olive tree pruning (OTP), olive leaves (OL), olive stone (OS), and extracted olive pomace (EOP). These lignocellulosic materials have varying compositions and potential utilization strategies within a biorefinery context. The aim of this work was to carry out an integral analysis of the aqueous extractives fraction of these biomasses. Several analytical methods were applied in order to fully characterize this fraction to varying extents: a mass closure of >80% was reached for EOP, >76% for OTP, >65% for OS, and >52% for OL. Among the compounds detected, xylooligosaccharides, mannitol, 3,4-dihydroxyphenylglycol, and hydroxytyrosol were noted as potential enhancers of the valorization of said by-products. The extraction of these compounds is expected to be more favorable for OTP, OL, and EOP, given their high extractives content, and is compatible with other utilization strategies such as the bioconversion of the lignocellulosic fraction into biofuels and bioproducts.

Highlights

Lignocellulosic biomass residues derived from agroindustries represent a valuable alternative source of material for the production of biofuels and bioproducts, which could replace those coming from conventional fossil sources
This paves the way for a sequential valorization of these biomasses that several researchers have studied previously: a first extraction step where these valuable compounds (e.g., DHPG, mannitol) are obtained, followed by a bioconversion step where the structural carbohydrates are transformed into biofuels and/or bioproducts
This strategy seems to be more suitable for olive tree pruning (OTP), olive leaves (OL), and extracted olive pomace (EOP), being the total amount of extractives more than 20% of the whole biomass, while for olive stones (OS), it may not be as profitable

Summary

Introduction

Lignocellulosic biomass residues derived from agroindustries represent a valuable alternative source of material for the production of biofuels and bioproducts, which could replace those coming from conventional fossil sources. The olive oil industry constitutes a large sector in Mediterranean countries, both culturally and economically: in Spain, a total of 2,733,620 ha were used in 2019 for the cultivation of olive trees, 60% of the total surface being concentrated in the southern region of Andalusia [1], for a total production of almost 6 Mt of olive biomass [2]. This industry comprises several activities such as olive tree cultivation, olive collection, production of olive oil, and extraction of olive oil pomace. Each of these by-products (see Figure 1) has unique characteristics, collection methods, and in the last years novel strategies for their valorization have emerged, making the term “residue” no longer suitable for them.

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